This invention relates to novel intermediates useful for the preparation of the well-known herbicide N-phosphonomethylglycine, and more particularly relates to the novel compounds (phosphonomethyl)perfluoroalkyl sulfonates.
N-phosphonomethylglycine, known in the agricultural chemical art as glyphosate, is a highly effective and commercially important phytotoxicant useful in controlling the growth of germinating seeds, emerging seedlings, maturing and established woody and herbaceous vegetation and aquatic plants. Glyphosate and its salts are conveniently applied in an aqueous formulation as a post-emergent phytotoxicant, or herbicide, for the control of one or more annual or perennial weed species. Such compounds are characterized by broad spectrum activity, i.e., they control the growth of a wide variety of plants.
Hershman, U.S. Pat. No. 3,969,398, describes a process for preparing glyphosate in which iminodiacetic acid is reacted with formaldehyde and phosphorous acid to produce N-phosphonomethyliminodiacetic acid as an intermediate, which is then oxidized to produce glyphosate.
Gaertner, U.S. Pat. No. 3,927,080, describes the production of glyphosate by the acid hydrolysis of N-t-butyl-N-phosphonomethylglycine or its esters. Tertiary butylamine is reacted with a bromoacetate ester to produce an ester of N-t-butylglycine which is in turn reacted with formaldehyde and phosphorous acid to produce the N-t-butyl-N-phosphonomethylglycine precursor.
Ehrat, U.S. Pat. No. 4,237,065, describes a process in which N-phosphonomethylglycine is prepared starting from glycine, formaldehyde and a tertiary base in an alcoholic solution. After completion of the reaction, a dialkylphosphite is added and the reaction product is hydrolyzed and then acidified to precipitate the product.
Creary et al, in J. Org. Chem., 50, 1985, pp. 2165-2170, discloses the triflate derivative of diethyl-(1-hydroxyethyl)phosphonate, but does not disclose any use for such compounds. Although such compounds are within the same general class of chemistry as the ones described herein, the structures are far different, and again no utility is disclosed.
Although satisfactory processes for the preparation of N-phosphonomethylglycine are disclosed in the above references and other references in the prior art, there is a need for yet other processes to prepare N-phosphonomethylglycine, especially processes that provide such a product in high yields and under mild reaction conditions. In addition, the compounds of this invention can also be used to prepare other amino-phosphorus compounds.